This invention relates to edge smoothing of digitally generated images and more particularly employing a variable rise time to blend adjacent intensities.
Heretofore, digital image generated (DIG) displays exhibited a "staircase" effect along face edges caused by the discrete changes in video intensity at specific X locations inherent in digital data. Horizontal edges (slope=0) were unaffected by this digital characteristic because they involved a single scanline (delta Y=0) with a single step at the start of the edge. As the horizontal edge was tilted upward or downward (delta Y.noteq.0) steps appear, one step for each horizontal scanline encompassed by the delta Y for that edge. As the edge approached a vertical position (slope approaches infinity) the steps increase in number but also become much smaller in amplitude (delta X approaches 0) and hence less visible. Previous techniques to smooth sloping edges involved massaging the digital data to provide a series of smaller step changes in intensity instead of a single step change. The resulting family of adjacent stair steps were less visible than the unsmoothed single stair case.